Gravitational settling in solar models

Calculations of the effects of gravitational settling and atomic diffusion in the solar models are presented with the aim of constraining the actual amount of gravitational settling that has occurred in the sun. Most of the discrepancies between the results of previous studies are explained. The observed solar Li abundance is used to constrain the amount of turbulent mixing below the solar convection zone, and a lower limit is set to the amount of gravitational settling in the sun. Comparison of the different formulations for calculating diffusion velocities used in previous studies shows that, for solar models, the differences in these formulations are too small to explain the variation in results found in these studies. Of the total increase in the central He mass fraction during evolution to the solar age, only about 0.013 out of the total increase of about 0.37 is found to be due to gravitational settling.